The present invention relates generally to a grounding switch. More particularly, the present invention relates to a grounding switch with a fixed switch piece attached to an equipment part to be grounded and with a switch piece displacable relative to the fixed switch piece by a drive with the switch pieces partially forming a switch-piece overlap in their closed position.
A grounding switch of this type is disclosed in German Auslegeschrift No. 2,155,398. This grounding switch is a manual grounding device, but is not intended for switching high powers. To avoid switching the grounding switches with high power, special bypass circuits are used or the grounding switch is replaced by a load breaker switch with sufficient breaking capacity. However, these measures make the switchgear having the grounding switches more expensive.
An object of the present invention is, therefore, to provide a grounding switch which is relatively simple in construction such that, while maintaining its geometrical dimension, it can switch even large currents such as short-circuit currents.
Numerous advantages are obtained by the present invention. For example, with a switch according to the present invention, the breaking capacity is improved, without increasing the switch dimensions. Also, when a grounding switch according to the present invention is cut out, the breaking current from the main contacts or the normal current path commutates safely from the outside into the center of the grounding switch and inwards to sparking contacts. In other words, there is a firm contact connection between the sparking contacts even through the main contacts have already separated. In the case of extreme loads, a switch according to the present invention meets the safety requirements since a circuit-breaking arc cannot burn from the center of the switch outwards and thus against a shield of the main contact or contacts. In other words, during circuit-breaking, the current or the contact separation is forced into the center of the contact system or the contact zone, once the main contacts have opened.
In comparison with known grounding switches, the switch according to the present invention switches larger currents without the switch pieces being overloaded as a result and without a significant increase in the overall dimensions of the switch. Overloading is substantially eliminated since the arc time is considerably reduced according to the invention. Moreover, the components required for such an improvement in the breaking capacity of the grounding switch are not only especially simple, reliable to operate and sturdy, but are also relatively few in number.
According to a further aspect of a grounding switch according to the present invention, the simple assembly and removal and, consequently, simple exchangability of the individual parts of the contact system is achieved. Further, the advantageous interaction of the individual parts is achieved without a special design of these parts. In particular, radial commutation contacts or a complex contacting of the sparking contacts is not required.
Further advantages to the grounding switch according to the present invention includes less expensive production costs and simplified construction. Also, the intervals between regular maintenance and inspection of the switch are not reduced. Still further, a compact and small construction is possible with a switch according to the present invention.